[PATCH 1/4] ARM: lds: place EFI runtime code and data in separate PT_LOAD segments

[Ahmad Fatoum]

From: Ahmad Fatoum <a.fatoum at barebox.org>

EFI runtime services support was added before barebox proper was made an
ELF and back then it proved too cumbersome to have two non-adjacent text
areas for each of the boot-time and run-time portions.

Now that barebox proper is an ELF, let's move the EFI runtime data and
text each into its own segment with the appropriate segment flags, so
pbl_mmu_setup_from_elf() can apply the correct protections.

The runtime sections are also moved between rodata and data rather than
at the end of the image: sections in a PT_LOAD must be contiguous, so in
the old position .bss would have had to move into the efirt_data
segment, inflating its p_memsz by all of barebox's bss, which would make
a BSS worth of memory unusable by the running kernel.

This does not yet introduce a functional change:
without ARM_MMU_PERMISSIONS, all cached mappings remain RWX.

Assisted-by: Claude:fable-5
Signed-off-by: Ahmad Fatoum <a.fatoum at barebox.org>
---
 arch/arm/lib32/barebox.lds.S      | 12 +++++++++---
 arch/arm/lib64/barebox.lds.S      | 12 +++++++++---
 include/asm-generic/barebox.lds.h |  6 ++++--
 3 files changed, 22 insertions(+), 8 deletions(-)

diff --git a/arch/arm/lib32/barebox.lds.S b/arch/arm/lib32/barebox.lds.S
index 02db3b9790b7..e5ef2d045218 100644
--- a/arch/arm/lib32/barebox.lds.S
+++ b/arch/arm/lib32/barebox.lds.S
@@ -13,6 +13,10 @@ PHDRS
 	text PT_LOAD FLAGS(5);		/* PF_R | PF_X */
 	rodata PT_LOAD FLAGS(4);	/* PF_R */
 	dynamic PT_DYNAMIC FLAGS(4);	/* PF_R */
+#ifdef CONFIG_EFI_RUNTIME
+	efirt_text PT_LOAD FLAGS(5);	/* PF_R | PF_X */
+	efirt_data PT_LOAD FLAGS(6);	/* PF_R | PF_W */
+#endif
 	data PT_LOAD FLAGS(6);		/* PF_R | PF_W */
 }
 
@@ -63,6 +67,9 @@ SECTIONS
 
 	__end_rodata = .;
 	_etext = .;
+
+	BAREBOX_EFI_RUNTIME
+
 	_sdata = .;
 
 	.data : { *(.data*) } :data
@@ -73,8 +80,6 @@ SECTIONS
 
 	_edata = .;
 
-	BAREBOX_EFI_RUNTIME
-
 	.image_end : { *(.__image_end) } :data
 
 	. = ALIGN(4);
@@ -94,4 +99,5 @@ SECTIONS
 	_barebox_image_size = __bss_start;
 }
 
-NOCROSSREFS_FROM(.efi_runtime)
+NOCROSSREFS_FROM(.efi_runtime.text)
+NOCROSSREFS_FROM(.efi_runtime.data)
diff --git a/arch/arm/lib64/barebox.lds.S b/arch/arm/lib64/barebox.lds.S
index 1dddd6d1a942..a06a078d4142 100644
--- a/arch/arm/lib64/barebox.lds.S
+++ b/arch/arm/lib64/barebox.lds.S
@@ -12,6 +12,10 @@ PHDRS
 	text PT_LOAD FLAGS(5);		/* PF_R | PF_X */
 	rodata PT_LOAD FLAGS(4);	/* PF_R */
 	dynamic PT_DYNAMIC FLAGS(4);	/* PF_R */
+#ifdef CONFIG_EFI_RUNTIME
+	efirt_text PT_LOAD FLAGS(5);	/* PF_R | PF_X */
+	efirt_data PT_LOAD FLAGS(6);	/* PF_R | PF_W */
+#endif
 	data PT_LOAD FLAGS(6);		/* PF_R | PF_W */
 }
 
@@ -43,14 +47,15 @@ SECTIONS
 
 	__end_rodata = .;
 	_etext = .;
+
+	BAREBOX_EFI_RUNTIME
+
 	_sdata = .;
 
 	.data : { *(.data*) } :data
 
 	_edata = .;
 
-	BAREBOX_EFI_RUNTIME
-
 	.image_end : { *(.__image_end) } :data
 
 	. = ALIGN(4);
@@ -61,4 +66,5 @@ SECTIONS
 	_barebox_image_size = __bss_start;
 }
 
-NOCROSSREFS_FROM(.efi_runtime)
+NOCROSSREFS_FROM(.efi_runtime.text)
+NOCROSSREFS_FROM(.efi_runtime.data)
diff --git a/include/asm-generic/barebox.lds.h b/include/asm-generic/barebox.lds.h
index 008217e808cb..c672894ad502 100644
--- a/include/asm-generic/barebox.lds.h
+++ b/include/asm-generic/barebox.lds.h
@@ -157,7 +157,7 @@
 #ifdef CONFIG_EFI_RUNTIME
 #define BAREBOX_EFI_RUNTIME			\
 	. = ALIGN(4096);			\
-	.efi_runtime : {			\
+	.efi_runtime.text : {			\
 		__efi_runtime_start = .;	\
 		__efi_runtime_text_start = .;	\
 		*(.efi_runtime.text*)		\
@@ -166,12 +166,14 @@
 		*(.efi_runtime.rodata*)		\
 		__efi_runtime_rodata_stop = .;	\
 		. = ALIGN(4096);		\
+	} :efirt_text				\
+	.efi_runtime.data : {			\
 		__efi_runtime_data_start = .;	\
 		*(.efi_runtime.data*)		\
 		*(.efi_runtime.bss*)		\
 		__efi_runtime_data_stop = .;	\
 		__efi_runtime_stop = .;		\
-	}					\
+	} :efirt_data				\
 	. = ALIGN(4096);
 #else
 #define BAREBOX_EFI_RUNTIME
-- 
2.47.3